Refrigerant System and Method of Operating the Same

ABSTRACT

The present disclosure provides a refrigerant system that comprises a compressor, a main refrigerant circuit, an economizer refrigerant circuit, and a bypass refrigerant circuit. The refrigerant system further comprises a single refrigerant flow control device switching between different operational modes to provide various degree of system unloading in operation. The present disclosure also provides a method of operating the refrigerant system.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

This disclosure relates to refrigerant systems. More particularly, thisdisclosure relates to refrigerant systems having economizer circuits andmethods of operating such refrigerant systems.

2. Discussion of the Related Art

Refrigerant systems are utilized to control the temperature and humidityof air in various environments to be conditioned. Typically, refrigerantsystems include a refrigerant that is compressed in a compressor anddelivered to a heat rejection heat exchanger. Although, as known, theheat rejection heat exchanger is a condenser for subcriticalapplications and a gas cooler for transcritical applications, forsimplicity, it will be referred to as a condenser throughout thedisclosure. In the condenser, heat is exchanged between outside ambientair (or other cooling media) and the refrigerant. From the condenser,the refrigerant passes to an expansion device, in which the refrigerantis expanded to a lower pressure and temperature, and is then passedthrough an evaporator. In the evaporator, heat is exchanged between therefrigerant and the indoor air, which is delivered into the environmentto be conditioned. When the refrigerant system is in operation, theevaporator cools the air that is being supplied to the conditionedenvironment. In addition, as the temperature of the air is lowered,usually moisture is also taken out of the air. In this manner, thehumidity level of the air can also be controlled.

Enhancement of system efficiency is one of the foremost concerns in theair conditioning and refrigeration industry. One of the optionsavailable to the refrigerant system designer to increase systemefficiency is a so-called economizer cycle. When the economizer circuitis activated, at least a portion of the refrigerant flowing from thecondenser is tapped and passed through an economizer expansion deviceand then to an economizer heat exchanger. This tapped refrigerant coolsa main refrigerant flow that also passes through the economizer heatexchanger. The tapped refrigerant leaves the economizer heat exchangerusually in a vapor state and is injected back into the compressor at anintermediate compression point. The main refrigerant is additionallycooled after passing through the economizer heat exchanger and thenflown through a main expansion device and to the evaporator. This mainrefrigerant flow will provide a higher capacity and/or efficiency, dueto extra cooling obtained in the economizer heat exchanger. Aneconomizer circuit thus provides enhanced system performancecharacteristics. As also known, there are several economizer circuitconfigurations that provide similar enhanced system operationalfunctionality. For instance, the economizer flow can be tapped from themain refrigerant flow downstream (instead of upstream) of the economizerheat exchanger. Also, a flash tank, essentially representing a 100%effective economizer heat exchanger, may be utilized instead to providesimilar functionality.

As known, to increase part-load efficiency, many refrigerant systems maybe equipped with the unloading features. In particular, one of suchunloading options available for economized refrigerant systems is abypass unloading, when at least a portion of partially compressedrefrigerant is bypassed from an intermediate compression point to thecompressor suction. It has been determined by the present disclosurethat many current economized refrigerant systems, and especially thesystems incorporating unloading functionality, require extra refrigerantcycle and control hardware, which add to the cost and complexity of therefrigerant systems utilizing such circuits. In addition, it has beendetermined by the present disclosure that the cost and complexity ofprior art economized refrigerant systems make it difficult and expensiveto retrofit existing refrigerant systems with economizer circuits.

Accordingly, there is a need for refrigerant systems and methods ofoperating such systems that will mitigate these and other disadvantagesof currently available economized refrigerant systems.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a refrigerant system. The refrigerantsystem comprises a compressor having a suction port and an intermediateport, a main refrigerant circuit, an economizer refrigerant circuit, abypass refrigerant circuit, and a refrigerant flow control device. Therefrigerant flow control device has at least two positions, with a firstposition providing fluid communication between the economizerrefrigerant circuit and at least one of the suction compressor port andthe intermediate compressor port, during an economized mode ofoperation. A second position provides fluid communication between theintermediate port and the suction port through the bypass refrigerantcircuit, during a bypass mode of operation. Additionally, therefrigerant flow control device may have a third position, at leastpartially isolating the economizer refrigerant circuit and the bypassrefrigerant circuit from the main refrigerant circuit, during a normalmode of operation. The compressor may be a single compression device, ora pair of compressors connected in sequence, so that the discharge portof the first compression stage is connected to a suction port of thesecond compression stage. In the latter case, the intermediatecompressor port is a point on the refrigerant line connecting the twocompression stages.

The present disclosure also provides a method for operating arefrigerant system. The method comprises: selectively controlling asingle refrigerant flow control device to provide the refrigerant flowthrough the economizer circuit, during an economized mode of operationof the refrigerant system, and to provide the refrigerant flow throughthe bypass circuit, during a bypass mode of operation of the refrigerantsystem. The method may include an additional step of controlling thesame refrigerant flow control device to provide the refrigerant flowthrough the main refrigeration circuit, and not through the economizerrefrigerant circuit or bypass refrigerant circuit, during a normal modeof operation of the refrigerant system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic drawing of a refrigerant system according tothe present disclosure; and

FIG. 2 shows a schematic drawing of a second embodiment of a refrigerantsystem according to the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a refrigerant system 10 according to the presentdisclosure is shown. Refrigerant system 10 has a refrigerant flowcontrol device 12 which is in communication with a controller 14.Controller 14 may be a main controller for refrigerant system 10, or aseparate auxiliary controller. In one embodiment, flow control device 12is a three-way valve and is controlled by controller 14 to selectivelyplace a main refrigeration circuit 16 in fluid communication with aneconomizer refrigerant circuit 18 or a bypass refrigerant circuit 20.Flow control device 12 may have an additional position to isolate mainrefrigerant circuit 16 from economizer refrigerant circuit 18 and bypassrefrigerant circuit 20.

Refrigerant flow control device 12 may regulate the flow of arefrigerant (not shown) through economizer refrigerant circuit 18 and/orbypass refrigerant circuit 20, with either modulated or pulsed methodsof control. Flow control device 12 may also mix refrigerant flows fromthe economizer refrigerant circuit 18 and the bypass refrigerant circuit20 in various proportions in a single refrigerant stream.

Therefore, refrigerant system 10 advantageously has a single refrigerantflow control device 12 to provide at least two modes of operation forthe refrigerant system 10: an economized mode of operation and anunloaded mode of operation, unlike currently available refrigerantsystems that require at least two refrigerant flow control devices. Assuch, refrigerant flow control device 12 only occupies a single output(not shown) of controller 14, unlike the two or more outputs required byconventional refrigerant systems having more than one refrigerant flowcontrol device. Thus, the refrigerant system 10 of the presentdisclosure is less complex and less expensive to implement. Moreover,the present disclosure, due to the use of a single refrigerant flowcontrol device 12, allows existing refrigerant systems to be more easilyretrofitted with economizer refrigerant circuit 18 and bypassrefrigerant circuit 20 than currently available equipment.

Main refrigeration circuit 16 includes a compressor 22, a condenser 24,a main expansion device 26, and an evaporator 28 in serial fluidcommunication with one another. In a normal mode of operation ofrefrigerant system 10, controller 14 controls flow control device 12 toa first position (not shown) such that refrigerant from mainrefrigeration circuit 16 is isolated from both economizer refrigerantcircuit 18 and bypass refrigerant circuit 20. Here, and as is well knownto a person of ordinary skill in the art, compressor 22 drivesrefrigerant through discharge refrigerant line 30 to condenser 24, fromcondenser 24 through liquid refrigerant line 32 to main expansion device26, from main expansion device 26 to evaporator 28, and from evaporator28 through suction refrigerant line 36 and back to compressor 22.Condenser 24 is in a heat exchange relationship with outside air 38,while evaporator 28 is in a heat exchange relationship with a fluid tobe conditioned 40, such as air delivered to a climate-controlled space.It should be noted that instead of outside air 38, other cooling media(such as, for example, circulating water or a glycol solution) can beused to cool the refrigerant in condenser 24.

For refrigerant system 10, the normal mode of operation may be optional,in addition to an economized and bypass modes of operation describedbelow. Therefore, refrigerant flow control device 12 may have anoptional position to provide a refrigerant flow through mainrefrigeration circuit 16, and to isolate this main refrigerant circuit16 from economizer refrigerant circuit 18 and bypass refrigerant circuit20, during a normal mode of operation of the refrigerant system 10.

Also as shown in FIG. 1, refrigerant system 10 comprisesperformance-enhancing economizer refrigerant circuit 18. Economizerrefrigerant circuit 18 includes an economizer expansion device 42 and aneconomizer heat exchanger 44. In an economized mode of operation,economizer expansion device 42 is in fluid communication with a liquidrefrigerant line 32 of main refrigerant circuit 16 via a tap refrigerantline 46. Further, economizer heat exchanger 44 is in serial fluidcommunication with expansion device 42, which is in turn in serial fluidcommunication with refrigerant flow control device 12, via an economizerrefrigerant line 50. In an economized mode of operation, flow controldevice 12 is also fluidly connected to an intermediate compressor port56 via an intermediate pressure refrigerant line 58.

Flow control device 12 can be controlled to a second position bycontroller 14 to place economizer refrigerant circuit 18 in fluidcommunication with main refrigerant circuit 16, so that at least aportion of refrigerant in main refrigerant circuit 16 flows througheconomizer refrigerant circuit 18, and into intermediate port 56 and/orsuction port 54 of the compressor 22. As shown, the refrigerant flowsthrough a tap refrigerant line 46, economizer expansion device 42,economizer heat exchanger 44, economizer refrigerant line 50, andrefrigerant flow control device 12 in sequence. When controller 14controls refrigerant flow control device 12 such that an economizerrefrigerant flow passes from main refrigerant circuit 16 to economizercircuit 18, refrigerant system 10 operates in an economized mode,discussed in further detail below.

Refrigerant flowing through main refrigerant circuit 16 in liquidrefrigerant line 32 also passes through economizer heat exchanger 44,and is in heat exchange relationship with refrigerant in tap refrigerantline 46 of economizer circuit 18. In economized mode of operation,refrigerant flowing through tap refrigerant line 46 is expanded ineconomizer expansion device 42 to a lower pressure and temperature, andused to further cool refrigerant in main refrigerant circuit 16 toenhance the capacity and efficiency of refrigerant system 10 as desired.Although the two refrigerant streams are shown flowing in the samedirection for illustration purposes, in practice, it is advantageous toarrange these flows in a counterflow configuration.

In the economized mode of operation, refrigerant flow control device 12may be controlled by controller 14 such that economizer refrigerant line50 of economizer refrigerant circuit 18 is in serial fluid communicationwith an intermediate pressure refrigerant line 58, and/or a bypassrefrigerant line 52. In this manner, refrigerant flows out of flowcontrol device 12, and takes one or both of two possible paths. Thefirst path is through intermediate pressure refrigerant line 58 and intointermediate port 56 of compressor 22. The second path is into bypassrefrigerant line 52, where it combines with the refrigerant flowing inrefrigerant suction line 36 and into suction port 54 of compressor 22.In this case, in the economizer mode of operation, flow control device12 can be selectively controlled so that all of the refrigerant flowingthrough economizer refrigerant line 50 of economizer circuit 18 flowsthrough intermediate pressure refrigerant line 58 and into intermediatecompressor port 56. Flow control device 12 can also be controlled sothat at least a portion of economizer circuit refrigerant in line 50 canbe diverted through bypass refrigerant line 52. The capability ofsimultaneously providing these two refrigerant flows can be obtainedthrough one of modulating or pulsating techniques. In the modulationtechnique, the refrigerant flow control device 12 provides variable sizerestrictions to the two refrigerant flows, thus simultaneously changingthe hydraulic resistances and controlling the amount of refrigerantdelivered into the suction and intermediate ports. In the pulse widthmodulation control, refrigerant flow control device 12 is rapidlyswitched from one economized mode of operation to the other.

Flow control device 12 can also be controlled to a third position bycontroller 14, placing refrigerant system 10 in a bypass unloaded modeof operation. In this mode of operation, refrigerant flows out ofintermediate port 56 of compressor 22 and into bypass refrigerantcircuit 20, i.e. through intermediate pressure refrigerant line 58 andbypass refrigerant line 52, before merging with the refrigerant insuction refrigerant line 36 and traveling back into suction port 54 ofcompressor 22. In bypass unloaded mode of operation, bypass refrigerantcircuit 20 is isolated from economizer refrigerant circuit 18 but is influid communication with main refrigerant circuit 16. Similarly to theabove description, refrigerant flow control device 12 can be controlledto regulate refrigerant flow by modulation or pulsation means.

Refrigerant flow control device 12 can also have a fourth position,during an economized/bypass mode, which puts the economizer and bypasscircuits in fluid communication with each other. The economizedrefrigerant flow from economizer refrigerant line 50 is combined withthe bypass refrigerant flow from intermediate pressure refrigerant line58 to be routed to bypass refrigerant line 52. Various flow combinationscan be provided by precise positioning of refrigerant flow controldevice 12, as will be discussed in further detail below.

Refrigerant line 58 can comprise two separate refrigerant lines, andintermediate port 56 of compressor 22 can comprise two separateintermediate ports, so that one of them is used during economized modeof operation, and the other is used during bypass unloaded mode ofoperation. Further, compressor 22 may be a single compressor unitcomprising two sequential compression stages or two compressorsconnected in sequence with an intermediate port located in between thetwo compressors.

Refrigerant flow control device 12 can be, for instance, of piston orrotary type, where controlling an alignment of valve openings withcorresponding refrigerant lines provides a desired mode of operation forrefrigerant system 10.

The mode of operation most desirable for refrigerant system 10 candepend on the required load on compressor 22, which will be a functionof the ambient temperature and the desired amount ofcooling/dehumidification in the climate-controlled space to beconditioned. Based on these parameters, controller 14 can selectivelyposition or adjust refrigerant flow control device 12 accordingly tomatch the thermal load demands in the conditioned space. For example, atmoderate levels of thermal demands, controller 14 can positionrefrigerant flow control device 12 in the first position as describedabove, placing refrigerant system 10 in a normal cooling mode ofoperation. At high levels of thermal demand in the conditioned spaceand/or at high ambient temperatures, controller 14 can positionrefrigerant flow control device 12 into the second position describedabove, placing refrigerant system 10 in an economized mode of operation.At low ambient temperatures and/or when there is a low demand forcooling, refrigerant flow control device 12 can be placed into the thirdposition, operating refrigerant system 10 in a bypass mode. The bypassmode can be advantageous in that at least a portion of the refrigerantin compressor 22 is not compressed fully, thus reducing the amount ofwork performed by the compressor and improving operational efficiency ofrefrigerant system 10.

As shown in Table 1 below, various combinations of operational modesdescribed above provide intermediate levels of loading and unloading forcompressor 22 that allow for refrigerant system 10 to precisely matchthermal load demands in the climate-controlled space. As stated hereabove, refrigerant flow control device 12 and controller 14 should becapable to provide this functionality. Thus, the present disclosure hasadvantageously disclosed a single refrigerant flow control device 12providing various combinations of operational modes for refrigerantsystem 10 at reduced complexity, cost, maintenance and improvedreliability.

As is shown in Table 1, refrigerant system 10 may have at least ninedifferent configurations. For example, in configuration #1, refrigerantsystem 10 is capable of operating in all of the four modes describedabove. In configuration #2, refrigerant system 10 can operate in normal,bypass, and economizer modes only, and so on. Thus, refrigerant system10 can be customized to the particular needs of a customer andapplication requirements.

TABLE 1 1 2 3 4 5 6 7 8 9 Normal X X X X X Bypass X X X X X X EconomizerX X X X X X Economizer with Bypass X X X X X X X

It should be noted that refrigerant flow control devices referred toherein as closed include refrigerant flow control devices such as valveswhich are substantially closed so as to prevent meaningful flowtherethrough, such that the circuits containing the valves aresubstantially inactive, and refrigerant flow control devices referred toas open include those which are substantially open so as to allowmeaningful flow therethrough, such that the circuits containing theserefrigerant flow control devices are substantially active.

It should be recognized that refrigerant system 10 is shown in FIG. 1,by way of example only, as having tap refrigerant line 46 of economizercircuit 18 selectively taping at least a portion of refrigerant fromliquid refrigerant line 32 of main refrigeration circuit 16 upstream ofthe first refrigerant pass through economizer heat exchanger 44. Ofcourse, it is contemplated by the present disclosure for economizercircuit 18 to be located anywhere in main refrigeration circuit 16 aslong as economizer heat exchanger 44 is positioned upstream of mainexpansion device 26 and downstream of condenser 24. For example, andreferring to FIG. 2, refrigerant system 10 is shown including taprefrigerant line 46 of economizer circuit 18 selectively taping at leasta portion of refrigerant from liquid refrigerant line 32 of mainrefrigeration circuit 16 downstream of the first pass through economizerheat exchanger 44. As was mentioned above, an economizer cycle with aflash tank may be equally utilized as well.

It should be pointed out that many different compressor types could beused in this invention. For example, scroll, screw, rotary, orreciprocating compressors can be employed. The refrigerant systems thatutilize this invention can be used in many different applications,including, but not limited to, air conditioning systems, heat pumpsystems, marine container units, refrigeration truck-trailer units, andsupermarket refrigeration systems.

While the present disclosure has been described with reference to one ormore exemplary embodiments, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted for elements thereof without departing from the scope of thepresent disclosure. In addition, many modifications may be made to adapta particular situation or material to the teachings of the disclosurewithout departing from the scope thereof. Therefore, it is intended thatthe present disclosure not be limited to the particular embodiment(s)disclosed as the best mode contemplated, but that the disclosure willinclude all embodiments falling within the scope of the appended claims.

1. A refrigerant system comprising: a compressor having a suction portand an intermediate port; a main refrigerant circuit; an economizerrefrigerant circuit; a bypass refrigerant circuit; and a flow controldevice, wherein said flow control device comprises: a first positionputting said economizer refrigerant circuit in fluid communication withat least one of said suction port and said intermediate port of saidcompressor, during an economized mode of operation, and a secondposition putting said intermediate port of said compressor and saidsuction port of said compressor in fluid communication through saidbypass refrigerant circuit, during a bypass mode of operation.
 2. Therefrigerant system of claim 1, wherein said flow control device furtherhas a third position isolating said economizer refrigerant circuit andsaid bypass refrigerant circuit from said main refrigerant circuit,during a normal mode of operation.
 3. The refrigerant system of claim 1,further comprising a first controller in communication with said flowcontrol device.
 4. The refrigerant system of claim 3, wherein said firstcontroller controls the refrigerant system.
 5. The refrigerant system ofclaim 3, wherein said first controller is in communication with a secondcontroller, wherein said second controller controls the refrigerantsystem.
 6. The refrigerant system of claim 1, further comprising aneconomizer heat exchanger in fluid communication with said compressor,wherein at least a portion of a refrigerant flowing through said mainrefrigerant circuit is diverted through said economizer refrigerantcircuit at a point upstream of said economizer heat exchanger, duringsaid economized mode of operation.
 7. The refrigerant system of claim 1,further comprising an economizer heat exchanger in fluid communicationwith said compressor, wherein at least a portion of a refrigerantflowing through said main refrigerant circuit is diverted through saideconomizer circuit at a point downstream of said economizer heatexchanger, during said economized mode of operation.
 8. The refrigerantsystem of claim 1, wherein said flow control device further has a thirdposition placing said economizer refrigerant circuit and said bypassrefrigerant circuit in fluid communication with each other, and withsaid main refrigerant circuit, during an economized bypass mode ofoperation.
 9. The refrigerant system of claim 1, wherein said flowcontrol device adjusts proportions of a refrigerant flowing into saidsuction port and said intermediate port.
 10. The refrigerant system ofclaim 1, wherein when said flow control device is in said firstposition, said economizer refrigerant circuit is in fluid communicationwith only one of said suction port and said intermediate port.
 11. Therefrigerant system of claim 1, wherein said refrigerant flow controldevice adjusts refrigerant flow through either modulated or pulsedcontrol.
 12. The refrigerant system of claim 1, wherein said flowcontrol device further has a third position, putting said economizerrefrigerant circuit and said bypass refrigerant circuit in fluidcommunication.
 13. The refrigerant system of claim 12, wherein said flowcontrol device adjusts proportions of a refrigerant flowing through saideconomizer refrigerant circuit and said bypass refrigerant circuit. 14.The refrigerant system of claim 1, wherein said flow control device is arotary type flow control device, or a piston type flow control device.15. The refrigerant system of claim 1, wherein said intermediate port isa single port for accepting economized refrigerant flow from saideconomizer refrigerant circuit, and for discharging bypass refrigerantflow into said bypass refrigerant circuit.
 16. The refrigerant system ofclaim 1, wherein said intermediate port of said compressor comprises afirst port and a second port, wherein said first port accepts economizedrefrigerant flow from said economizer refrigerant circuit, and saidsecond port discharges bypass refrigerant flow into said bypassrefrigerant circuit.
 17. The refrigerant system of claim 1, wherein saidflow control device is a three-way valve.
 18. A method of operating arefrigerant system, comprising the steps of: controlling a refrigerantto flow through a main refrigerant circuit and an economizer refrigerantcircuit, but not a bypass refrigerant circuit, during an economizer modeof operation; and controlling said refrigerant to flow through said mainrefrigerant circuit and said bypass refrigerant circuit, but not saideconomizer refrigerant circuit, during a bypass mode of operation. 19.The method of claim 18, further comprising: controlling said refrigerantto flow through said main refrigerant circuit but not said economizerrefrigerant circuit and not said bypass refrigerant circuit during anormal mode of operation.
 20. The method of claim 18, furthercomprising: controlling said refrigerant to flow through said mainrefrigerant circuit, said economizer refrigerant circuit, and saidbypass refrigerant circuit during an economized bypass mode ofoperation.